Semiconductor devices containing integrated circuits (ICs) or discrete devices are used in a wide variety of electronic apparatus. The IC devices (or chips or discrete devices) comprise a miniaturized electronic circuit that has been manufactured in the surface of a substrate of semiconductor material. The circuits are composed of many overlapping layers, including layers containing dopants that can be diffused into the substrate (called diffusion layers) or ions that are implanted (implant layers) into the substrate. Other layers are conductors (polysilicon or metal layers) or connections between the conducting layers (via or contact layers). IC devices or discrete devices can be fabricated in a layer-by-layer process that uses a combination of many steps, including growing layers, imaging, deposition, etching, doping and cleaning. Silicon wafers are typically used as the substrate and photolithography is used to mark different areas of the substrate to be doped or to deposit and define polysilicon, insulators, or metal layers.
One type of semiconductor device, a metal oxide silicon field effect transistor (MOSFET) device, can be widely used in numerous electronic apparatus, including automotive electronics, disk drives and power supplies. Some MOSFET devices can be formed in a trench that has been created in the substrate. One feature making the trench configuration attractive is that the current flows vertically through the channel of the MOSFET. This permits a higher cell and/or current channel densities than other MOSFETs where the current flows horizontally through the channel and then vertically through the drain. The trench MOSFET devices contain a gate structure formed in the trench where the gate structure contains a gate insulating layer on the sidewall and bottom of the trench (i.e., adjacent the substrate material) with a conductive layer that has been formed on the gate insulating layer.